I. Technology Field
The present invention relates to medical devices, endoprostheses, stents, and methods for the manufacture and use of the same. More particularly, the devices of the present invention are configured to include a porous network that contains an elution rate controlling matrix carrying an active agent.
II. The Related Technology
Balloon angioplasty, either alone or followed by an endoprosthetic implantation, has become a commonplace interventional alternative to open heart surgery in those patients appropriate for such treatment. Endoprostheses are generally tubular members having a collapsed state suitable for insertion into a vessel and a deployed state in which the endoprosthesis is expanded to support the surrounding tissue and prevent at least local narrowing of the vessel. Several types of endoprostheses are known, including balloon expandable, self-expanding, and endoprostheses constructed from biostable springs.
Polymeric materials, for example, are commonly used in medical devices as matrices for the retention of therapeutic agents. These polymeric materials are typically applied as coatings to the medical devices, raising issues regarding coating adhesion, mechanical properties, cracking, delamination, and material biocompatibility. However, problems occur when mechanical forces are applied on an endoprosthesis during manufacture (e.g., crimping, endoprosthetic retention procedures, packaging etc.) as well as during actual use (e.g., unsheathing, catheter preparation, advancement through catheter and vasculature), which may result in damaging the polymeric coating. In addition, many polymers with desirable controlled release properties, like the family of biodegradable polymers based on polylactide, polyglycolide and their copolymers are difficult candidates for a polymeric endoprosthetic coating, because of poor adhesion to metals and/or poor elongation and brittle character.
There exists a need in the art for medical devices (specifically, drug eluting endoprostheses) capable of retaining a therapeutic agent in an endoprosthesis so that the drug may be eluted to a local region of the vessel wall in a controlled manner through pores in the endoprosthesis. Furthermore, an ideal medical device would incorporate agents within a polymer in protective pores to reduce or eliminate current aggressive manufacturing method problems or actual use to prevent physical damage of the medical device.